Control system for elevators



A. PI NTO CONTROL SYSTEM FOR ELEVATORS Nov. 9, 1937.

Filed Nov. 15 1936 LEVl-ilImG CONTROL T; v LLJLL 03412, INVENTOR ATTORNEY Patented Nov. 9.1937

' usirso STATES [PA ENT ar s I comer. svsm l amvs'roas m N. Y m to memes-w Otisllevatar Company ccrporationoi'NewJer-sey Application November 13,1986. Serial No. uosss 11 Claims.

The invention relates to control systems, and particularly to control systems for elevators.

In elevator control systems where a direct current motor is employed for raising and lowering the elevator car and is supplied with'current by a variable voltage direct current generator, the generator is required to operate over a wide range of E. M. 1''. values. varying from a maximum in one direction to a maximum in the other; During the slow speed operation in making a stop, the

generator is required to operate at low values of E. M. 1". Due to the residual flux of the gen erator field. the E. M. 1". values obtained for a given value of generator ileld current during the slowfmm operation vary considerably, depend-' ing upon the previous magnetic state of the machine. Such variations in I. M. F. values cause undesirable variations in the operation of the car in making a stop. These variations are particularly objectionable where self-levelling apparatus is employed for bringing the-car to an accurate stop regardless of whether the car overruns or underruns the landing. a

The principal object of the invention is overcome the eifects of residual flux.

The invention involves controlling the excitation of the generator during slow speedvoperation in such way that the generator voltage due to residual flux is reduced substantiallyto zero.

The invention willfbe described as applied to an elevator system in which self-levelling apparatus is provided to bring the car in stoppi to main generator during levelling. The auxiliary generator is provided with. a field winding which is connected'in circuit with the main fleld winding of the main generator. The armature of the 'auxiliary generator is connected in the circuit w'itlr the auxiliary field winding. Upon discomtinuation of the excitation of the main generator as thelevelling mechanism takes control, both generators are excited by residual flux due'to 'their previous excitation. .The characteristics of the auxiliary generator are such that it acts through the main generator auxiliary field wind-- ing to provide an excitation of the main generator which reduces the residual flux of the main generator substantially to zero. tion is superimposed upon the auxiliary field winding for causing the generation of sufficient voltaB? to bring the car to a landing level. Due to the compensation for residual flux-provided by the auxiliary generator. substantially the same generator voltage -is obtained for returning the car to the landing after an overrun as for bringing it to the landing upon an underrun, thereby assuring uniform levelling operation.

A general idea of the invention, its application to a self-levelling elevator installation, and the various features and advantages thereof will be Additional excitagained from the above statements. Other features and advantages of the invention will be apparent from the following description and ap-. pended claims.

-may'be added in making up the complete system and that such system is subject to many variatiqns. It is to be further understood that the invention is applicable to various types of elevator systems such as car switch control systems, push button control systems, and other systems employing a work motor supplied with current from the generator of a motor generator set.

' The electromagnetic switches have been designated as follows:

, Throughout the description which follows, these letters, in addition to the usual reference numer-.

'als. will be applied to the parts of the above enumerated switches. The numerals employed in designating the various elements of the wiring diagram are arranged in sequence. the lowest number appearing in the upper left hand corner of the drawing, with the succeeding numbers I erator The elevator car is designated w and its counterweight 55. The car is raised andlowered by means of cables passing over hoisting drum M, which in turn is drivenby elevator motor 390. The elevator car is held when at rest by means of an electromechanical brake, the coil of which is designated 50. The armature of the hoisting motor is designated ii, while its field Winding is designated Zl. The armature of the supply generator 32 for the hoisting motor is designated M, its main field winding 26, and its levelling field winding 3?. The driving motor for the generator armature is not shown. The residual compensation generator 35 is provided with a shunt field winding 341 and a main field winding 25, the main field winding being arranged in series with the main generator field winding 26. The driving motor for armature 36 of the residual compensation generator is not shown. It may be driven by a motor separate from the main gendriving motor.- Discharge resistances which may be provided for certain of the field windings are not shown. H, i2, ill and 33 designate current supply wires which may be connected to the same or different sources.

Up main direction switch U is operated to start the car in the up direction while down main direction switch D is operatedto start the car in the down direction. The actuating coils 52 and 5? of these switches are controlled by contacts 5!! and 56 respectively on the main control. These contacts may be contacts of electromagnetic switches or may be operated manually. Up direction switch U, upon operation, closes contacts l5 and 2d, connecting field windings 25 and 2t across supply wires ii and it for current supply in a direction to cause the generation of voltage by generator 32 of a polarity to cause operation of the car in the up direction. The down direction switch, upon operation, closes contacts ill and 3H, reversing the connections of the field windings to the supply wires, thereby causing the generation of voltage to operate the car in the down direction. The brake is released to permit starting of the car upon operation of either direction switch, the circuit for the brake release coil til being established by contacts 62 upon operation of the up direction switch and by contacts t l upon operation of the down direction switch.

The car, upon being started, is accelerated by increasing the voltage of the generator and is retarded by decreasing the voltage of the generator. means of a resistance it in series with generator field winding 26, steps 29, Hand Q3 of this resistance being short-circuited in sequence by contacts it, Ml and it? to bring the car up to full speed and being reinserted in reverse sequence to slow the car down to a slow speed preparatory to stopping.

The levelling mechanism acts to bring the car to an exact landing level in case it underruns cally, as by the cooperation of cams with rollers on operating arms for the. contacts, by relative movement of thecamsand rollers, or inductively,

as by the magnetic cooperation of electromag-.

netic switch structure with magnetizable plates,

This control is illustrated as effected by aooavoa by relative movement or the structure and the plates, or in any other suitable way. Contacts 66 and it are fast speed levelling contacts while contacts ii and it are slow speed levelling contacts. These contacts act through the levelling electromagnetic switches to provide two speed levelling. A two speed levelling zoneis provided on each side of each landing. Contacts 66 and ii engage as the car enters the up fast speed levelling zone for the landing at which a stop is being made. As the car enters the up slow speed levelling zone, contacts fit separate. Con tacts ll separate just before the car reaches the exact floor level; Similarly, contacts 15 and i3 engage as the car enters the .down fast speed levelling zone for the landing at which a stop is being made. As the car enters the down slow speed levelling zone, contacts 115 separate. Contacts l3 separate just before the car reaches the exact floor level.

Assume that the car hasbeen running in the up direction, that slow down has been initiated preparatory to bringing the car to 'a stop at a.

landing, and that the levelling mechanism has been rendered effective. .Upon arrival of the car in the up fast speed levelling zone for the landing, up levelling switch contacts 66 and ii are engaged. The engagement of contacts 66 completes a circuit for coiltl of fast speed levelling relay LFR. This relay operates to open its contacts it?) to prevent the energization of coil 65 of slow speed levelling switch LS. The engagement of contacts ii completes the circuit for coil 72 of up levelling direction switch LU. This switch closes contacts iii and to to prepare the circuit for levelling field winding 3'1] for current supply theretoin a direction to excite the generator for continued upward movement of the car. The up main direction. switch is maintained operated during slow down preferably until the car enters the fast speed levelling zone. Upon dropping out, the up main direction switch opens contacts i5 and 24 to deenergize generator main field winding 2% At the same time, however, lt closes contacts til to complete the circuit for generator levelling field winding 37. Thus the generator excitation for the levelling operation is provided by field winding ti, the EXOiiZfi'.

tion being such as to cause the car to run at a fast levelling speed. The brake is maintained released by contacts All of up levelling direction levelling relay. This relay, upon dropping out,

closes contactstt, which completes, through up main direction switch contacts til, now closed, and up levelling direction switch contacts 64, a

circuit for coil 65 of slow speed levelling switch LS. This switch operates to open contacts 45, inserting resistance it in the circuit for generator levelling field winding it. This reduces the excitation of the generator provided by field winding til, causing the car to run at a slow levelling speed.

Just before the car reaches an exactlevel with the landing, contacts H separate t deenergize coil T12 of the up levelling direction switch.' This switch drops out, opening contacts 16 and to deenergize levelling field winding 31. It also opens contacts 4"! to deenergize brake release coil iii. Thus, the brake is applied, bringing the car travel.

84 to prepare the circuit for levelling field winding 31 for current supply thereto in a direction to excite the generator for continued downward movement of the car. As in the case of the up main direction switch, the down main direction switch is maintained operated during slow down preferably until the car enters the fast speed levelling zone. main direction switch opens contacts l1 and 30 to deenergize generator main field winding 28 and at the same time closes contacts ii to complete the circuit for generator levelling field winding 31. Thus excitation for the generator isprovided by field winding 31 for the levelling operation to cause the car to run at a fast levelling speed. The brake is maintained released during levelling by contacts 53 of down levelling direction switch LD.

As the car enters the slow speed levelling zone, contacts l5 separate to cause the deenergization of fast speed levelling relay LFR and thus the operation of slow speed levelling switch L8] This switch operates to insert resistance 46 in the circuitfor field winding 31', reducing the generator excitation sufficlently to cause the car to run at a slow levelling speed. Just before the exact landing level is reached, contacts 133 separate,

causing the dropping out of the down'levelling direction switch LD. This switch opens contacts 82 and B5 to deenergize levelling field winding 37, and also openscontacts 53 to deenergize brake release coil 56. Thus the brake is applied, bringing the car to rest level with the landing.

In the event that the car, in. making a stop at a landing, overruns the floor, the levelling mocha nism acts to cause the car to he returned to the landing level. Assume, for example, that the car has been travelling in the up direction and, in making a stop at a landing, overruns the floor.

If the overrun extends into the down fast speed levelling zone, both contacts 55 and FE engage, causing the operation of down levelling direction switch Ll) and fast speed levelling relay LFR. Down levelling direction switch LD, by engaging contacts 53, 82 and 84,.causes the release of the brake and the application of voltage to levelling field winding 3? of a polarity to cause the car to be returned to the landing. As the down slow speed levelling zone is reached, contacts 15 sepso that slow speed levelling switch LSis operated immediately upon operation of the levelling direction switch. Thus'resistance 48 is inserted in circuit with field winding 31, causing the ear to be returned to the floor at slow levelling speed.

Upon dropping out, the down.

The armature 36 of residual compensation generator 35 is in series with generator levelling field winding 31,. This generator acts during levelling to compensate for the efiects of residual flux of the generator field. Due to the relatively low value of generator excitation for levelling, the

residual flux of the generator field forms a large percentage of the total flux and therefore affects the operation of the system very markedly. Unless its efiect is overcome, it causes the value of the excitation voltage generated, when the external exciting current is of the same value for returning the car to a fioor after an overrun as for causing it to continue to the 1100! during an underrun, to. be much less for returning the car to the floor than for causing. it to continue to the -floor during the underrun. Furthermore, the

value of these voltages may vary, depending upon the previous magnetic state of the machine, which in turn determines the shape 01 the hysteresis loop and thus the amount of residual flux. Such differences in voltage are undesirable under level from its main field winding 26 to its levelling field winding 31, 'or it may be driven all the time the main motor generator set is in operation. As field winding 25 of the residual compensation generator and field winding 25 of the main generator are connected in series, they are subject to the same current variations. At the instant field winding 28 is disconnected, there is a voltage generated by the main generator due to the residual flux of the generator field. There is also a voltage generated by the residual compeusa tion generator due to the residual flux: of its fie Since the same exciting current has been sup, to both field windings 25 and 25, the value at the residual voltage of the residual compensation generator is substantially proportional to that oi" the res dual voltage of the main generator. The residual compensation generator is designed that ii, upon disconnection of field windings 2S and 26 from the source, armature 36 is connected directly across field winding 3? in such way as produce a magnetizing force which opposes the residual flux of the main generator, the voltage of the main generator would be reduced zero.

Thus, with the armature of the residual com pensation generator connected in series with field winding 31, the residual voltage of the main gen erator is eliminated so that the application. of an external voltage to field winding 31' produces substantially the same value of fast speed level ling voltage for returning the car to the landing after an overrun as for bringing it to the floor during an underrun.

The insertion of resistance 46 in the circuit for field winding 81 for slow speed levelling, un

less counteracted, reduces the voltage applied to this field winding by the residual compensation generator due to the voltage drop across this resistance. To maintain the. residual compensation voltage at proper value to overcome the ef fects of residual flux at the time resistance 46 is'inserted, slow speed levelling switch LS, in

' generator.

' separate driving motor.

closes contacts til to connect shunt field winding '34 across armature at of the compensation gen- This shunt field winding is wound so that erator. I the self excitation of the generator produced thereby counteracts the voltage drop .across resistance it ,to such extent as to maintain the voltage of the compensation generator of proper value to compensate for residual flux of the main The direction of the excitation of shunt field winding 3d, being dependent upon the residual flux of the residual compensation generator 35 produced by field winding 25, is always correct. I I g It is to be understood that. in order to minimize circulating current in the motor armature-generator armature loop circuit when the car is stopped, main field winding it may be connected across armature it of the main generator in such way as to counteract the residual flux of the generator iield. Such arrangement is termed a suicide connection. Instead of thisarrangement, when the car is stopped armature tit may be connected directly across field winding till, this held winding being disconnected from supply mains ill and or and slow speed levelling switch LS being dropped out whenthe car is stopped. In such case, the effects of residual flux are overcome and the circulating current is reduced substantially to zero while the car is at rest, it being understood that the residual compensation generator is maintained in operation while the car is standing.

In case of polyphase alternating current supply 7 to the building in which the elevator is installed, power supply for wires i l and It may be obtained from an exciter which may be driven by the driving motor of the motor generator set or by a Wires ll and til also may be supplied from this exciter. On the other hand, wires ill and d3 may be supplied with current from a separate exciter, regardless of the type of power supply to the building or the manner in which current is supplied to wires it and iii. With such arrangement, a reduction in voltage for slow speed levelling may be obtained-by reducing the excitation of this separate exciter and the shunt field winding of the residual compensation generator maybe omitted.

It is to be understood that an arrangement may be provided forcompensating for variations in load on the elevator hoisting motor, particularly during levelling? Where wires it and at are supplied'i'rom a separate exciter, load compensation during levelling may be obtained by providing thisexciter with a separately excited load compensatingfleld winding connected across resistance in the loop circuit of the armature oi the elevator hoisting motor and the armature of the main generator. With the control or the generator voltage for fast and slow speed levelw ling eflectedby controlling the excitation of the separate exciter, proper load compensation is provided'by this oad compensating field windin for both levelling speeds. However, with resistwinding on the-main generator, rendered eflec-- tive only for the levelling operation. In case it is aoeavea desired to use this series field winding for load compensation for fast speed operation as well, another field *winding may be connected in the 'loop circuit of the armature of the elevator hoistoverrun.

Manyelevator control systems are very complex and admit of many variations. In applying the invention'to such control systems, variations in the manner in which the excitation of the generator is controlled may be made with the view of adapting the invention more readily to such control systems. lihese and other changes in the manner of controlling the generator excitation may be made which do not depart from the spirit and scope of the invention. It is therefore intended that all matter contained in the above description or shown in the accompanying drawing shall be interpretedas illustrative and not in a limiting sense.

What is claimed is:-

1. In combination; an elevator car; a direct current hoisting motor therefor; a'variable voltage generator for supplying current to said motor; means for variably exciting said generator in the operation of said car from one landing to another; and means for causing said car to operate at slow speed prior to stopping at a landing,

said last named means comprising means for ex-:

citing said generator in a direction to oppose the residual flux of the generator and in an amount, determined by the excitation of said generator during operation of the car to such landing, to

compensate for the residual flux and in addition age direct current generator for supplying cur-' rent to said motor; means for exciting said'gene ator-to efiect movement of said car from one la ding to another; and means for exciting said generator to cause the car to operate at a slow speed-to bring it to a level with the landing at which a stop is being made, said last named means comprising means for causing the excitation of said generator for such slow speed to be controlled in accordance with the excitation of said generator during said movement of said car to the landing at which the ,stop is being made to compensate for the residual flux of the generator.

'3. In combination; an elevator car; a direct current hoisting motor therefor; a main direct current, generator for supplying current to said motor; means for causing excitation of said main generator to eflect movement of said car from one landing to another; and means for causing excitation of said main generator to level the car with the landing at which" a stop is being made, regardless of whether the car overruns or underruns the landing, said last named means comprising an auxiliary direct current generator ,for exciting said main generator in a direction to oppose the residual flux of said main generator,

- proportion to the residual flux of said main genenter and to such extent as to reduce the voltage of the main generator due to residual flux substantiallyto zero.

4. In combination; an elevator car; a direct currenthoistingmotor' therefor; a main direct currentgenerator for supplyingcurrent to said motor; means for causing excitation of said main generator to effect movement of said car from one landing to another; and meansfor causing excitation of said main generator to level the car with the landing at which a stop is being made, regardless oi. whether the car overruns or underruns the-landing, said last named means comprising an auxiliary directvcurrent generator, means for exciting said auxiliary generator by residual fiu'x proportional to the residual fiux of said main generator and means for causing said auxiliary generator to excite said main generator in such way and to such extent as to reduce the voltage thereof due to residual fiux'substantially to zero. 5i In combination; an elevator car; a direct current hoisting motor therefor; a main direct current generator for supplying current to said motor; means for causing excitation ofsaid main generator to eflect movement said car from one landing to another; means for causing excitation of said main generator to level the car with vthe landing at which a stop is being made, regardless of whether the car overruns or underruns the landing; and means for overcoming the efiects of residual fiux oi said main generator during levelling, said last named means comprising an auxiliary direct current generator for controlling the excitation of said main generator during levelling and means for exciting said auxiliary generator in accordance with the previous excitation of said main generator,

En combination; an elevator car; a direct hoisting motor therefor; a main direct current generator for supplying current to said r, said 2 tor having a main field windesry field winding; means for of said main generator by said '5 to effect movement oi ,saidcar to another; and means for said main generator Toy said rig to level the car with the stop is being made, regardless e overruns or "undermine the .i to b, so last namedvmeans comprising an auxiliary direct current generator for exciting said auxiliary fleid winding in a direction to op pose resicuai of said main generator, and

' means for exciting said auxiliary generator in proportion to residual flux of said main gencrater mzch extent as to effect a reduc non of the voltage of the main generator due to i residual iiux substantially to zero.

'4'; in. combination; an. elevator car; a direct rrent hoisting motor therefor; a main direct current generator for supplying current to said motor, said generator having a main separately excited field winding and an auxiliary separately excited field winding; means for causing excitation of said main'generatcr by said main field winding to eflect movement of said car from one landing to another; means for causingexcitation of said main generator by said auxiliary field wlnding to level the car with the landin; at which a stop is being made, regardless of whether the car. overruns or undermine the landing; and means for overcoming the eflects of residual flux of said main generator during levelling, said last named means comprising ad auxiliary direct current generator for controlling the excitation of said auxiliary field winding and means for exciting said auxiliary generator in accordance with the previous excitation of said main generator.

8. In combination; an elevator car; a direct current hoisting motor therefor; a main direct current generator for supplying current to said for exciting said auxiliary field winding in adirection to oppose the residual flux of said main generator, said auxiliary generator having its armature connected in series with said auxiliary field winding, and its field winding connected for excitation in accordance with the excitation of said main field winding so as to excite said auxiliary generator during levelling by residual flux to such extent as to proyide excitation of the main generator which overcomes the residual flux of the main generator.

9. In combination; an elevator car; a direct current hoisting motor therefor; a direct current generator for supplying current to said motor, said generator having a main separately excited field winding and an auxiliary separately excited field winding; means for causing excitation of said generator by said main field winding to effect movement of said car from one landing to another; means for causing excitation of said generator by said auxiliary field winding to level the car with the landing at which a step is being made, regardless of whether the car overruns or underruns the landing; and means for overcoming the effects of residual flux of said generator during levelling, said last named means comprising a direct current generator having an armature connected in series with said auxiliary field winch 7 movement of said car from one landing to another; means for discontinuing excitation of said generator by said main field winding and for causing its excitation by said auxiliary field winding to level the car with the landing at which a stop is being made, regardless of whether the car overruns or underruns the landing; and means for overcomiiig the effects of residual flux of said generator during levelling, due to the previous excitation provided by said main field winding, said last named means comprising a direct current generator having an armature connected in series with said auxiliary field winding and a separately excited field winding connected in series with said main field winding.

11. In combination; an elevator car; av direct current hoisting motor therefor a direct current generator for supplying" current to said motor,

said generator having a main separately "excited field winding and an auxiliary separately excited field winding; means for connecting said main field winding to a source of direct current to efiect movement of said car from one landing to another; means i'or disconnecting said rnain field winding and for connecting said auxiliary field winding to a source of direct current to level the car with the landing at which a stop is being made regardless of whether the car overruns or underruns the landing; means for causing the car to operate at two different levelling speeds, dependent upon the distance or the car from saidlanding during the levelling operation, said means comprising resistance in series with said aarr aooaroa 1 held ding and means for short-circuiting said resistance to eflect a fast levelling speed and for removing said short-circuit to edect. a slow levelling s; and means for overcoming the eflects of residual flux oi said generator during levelling, said last named means comprising an auxiliary direct current generator having an armature connected in series with said auxiliary field windi, a separately excited field winding connected in series with said main field winding,

an additional field winding, and means for connecting said additional field winding across the armature oi said auxiliary generator while saidahort-cireuit for said resistance is removed.

@NY PINTO. 

